Differential brake control involves providing individual brake commands of different degree to respective wheels of a vehicle. In the case of aircraft, for example, pilots have the ability to control direction of the aircraft not only using nose wheel steering and rudder movement. The pilot may also control the direction by pushing the left and right brake pedals by differing amounts to effect differential braking with respect to the left and right wheels of the aircraft.
Generally speaking, to move a vehicle back to a centerline, it is necessary to turn, or yaw, the vehicle. In order to obtain a yaw, it is necessary to have a yaw rate. To obtain a yaw rate, it is necessary to apply a torque (moment) about the vertical axis of the vehicle. Differential brake control provides the capability to turn the vehicle by applying a torque via different amounts of braking to wheels on opposite sides of the vertical axis.
Accordingly, a pilot wishing to turn an aircraft during taxiing, landing, etc., can implement such turn by applying the above principles of differential brake control. The pilot presses individual brakes for left and right wheels by differing amounts in order to create the necessary torque to turn the plane. The rate and amount by which the braking to the left and right wheels differ determines how quickly and in what direction the aircraft will tend to turn.
The use of differential brake control in aircraft is an effective way to turn an aircraft. However, differential brake control in the past has been largely dependent on the pilot to implement such control manually by way of pressing the left and right brake pedals by differing amounts. There are three ways a pilot can initiate a turn. The pilot may lift one pedal and release the other the same amount to maintain the current deceleration. The pilot may push one pedal harder with the collateral effect of increasing overall deceleration. Conversely, the pilot may also desire to lift one pedal with the collateral effect of decreasing overall deceleration.
In view of the aforementioned shortcomings associated with conventional differential brake control, there is a strong need in the art for a brake control system capable of providing automated differential brake control. Still further, there is a strong need in the art for a brake control system operative to provide automated differential brake control in an aircraft independent of a pilot, such as in an unmanned aircraft. In addition, there is a strong need in the art for a brake control system that is less susceptible to differences in wheel speed due to asymmetries on the aircraft and in the environment.